Use of lubricating compositions to improve the cleanliness of a 4-stroke vehicle engine

ABSTRACT

The invention relates to the use of an alcohol of formula R—OH (I), in which R is a linear or branched saturated alkyl group with 10 to 36 carbon atoms, in a lubricant composition to improve the cleanliness of a 4-stroke vehicle engine.

The invention concerns the use of a lubricant composition to improve thecleanliness of a 4-stroke vehicle engine. More particularly, theinvention concerns the use of an alcohol in a lubricant composition toimprove the cleanliness of a 4-stroke vehicle engine.

Developments in engines and in the performance of engine lubricantcompositions are inextricably linked. The more engine design becomescomplex the higher the yield and optimisation of consumption, and thegreater the demand placed on engine lubricant compositions for whichperformance must be improved.

Very high compression inside engines, higher piston temperatures inparticular in the piston top segment, modern maintenance-free valvecontrols with hydraulic plungers, and very high temperatures in theengine space constantly place increasing demand on lubricants for modernengines.

The conditions of use of gasoline engines and diesel engines includeboth extremely short trips and long distances. The journeys travelled by80% of motor vehicles in Western Europe cover less than 12 kilometres,whereas vehicles clock up annual distances of up to 300 000 km.

Oil change intervals are also most variable, being 5 000 km for somesmall diesel engines and may extend up to 100 000 km for diesel enginesof modern commercial vehicles.

Lubricant compositions, and in particular lubricant compositions formotor vehicle engines, must therefore have improved properties andperformance levels.

In addition, 4-stroke vehicle engines require high cold startproperties.

One problem encountered when using known lubricant compositions concernsthe degradation and coking of the oils or additives used. Thesedegradation and coking phenomena may lead to clogging of the lubricatedparts, in particular inside a vehicle engine.

It is therefore necessary to provide lubricant compositions allowingimproved engine cleanliness in a 4-stroke vehicle engine. Theimprovement of engine cleanliness generally comprises reduced formationof deposits, in particular the formation of deposits at hightemperatures such as varnish, paint, carbon or coke deposits. Suchdeposits may form on hot surfaces of engine parts such as the bottom ofpiston grooves, turbocharger shafts or air compressors. The substancescontained in lubricant compositions may oxidize in contact with hotengine surfaces and generate the formation of insoluble products formingdeposits.

These deposits may foul the engine and cause problems of wear, seizure,sticking of segments and problems related to turbocharger rotation forexample. In general, additives of detergent type are used to improve thecleanliness of a 4-stroke vehicle engine.

Lubricant compositions are known from WO2015/179280 which compriseunsaturated fatty alcohols. However, this type of fatty alcoholsolidifies at temperatures in the region of 10° C. and therefore doesnot allow satisfactory cold start properties to be obtained.

There is therefore a need for lubricant compositions providing good coldstart properties.

These problems of fouling also concern the engines of hybrid ormicro-hybrid vehicles equipped with the “Stop and Start” system.

In vehicle engines and in particular 4-stroke engines, deposits (enginefouling) are due to ageing of the lubricant. On the contrary, in2-stroke marine engines, deposits are due to combustion of the mixtureof lubricant and fuel on account of the specificity of 2-stroke marineengine operation (the term expendable lubrication system is used).

It is therefore necessary for vehicle engines, in particular motorvehicle and particularly 4-stroke engines to provide lubricantcompositions able to withstand and especially undergo the least possiblechemical degradation when an engine is in use, to limit ageing of thelubricant composition and hence limiting of deposits. This does notprove to be necessary for marine engines since the lubricant will alwaysundergo combustion in the mixture with fuel.

It is therefore one objective of the present invention to providecompounds and a lubricant composition comprising these compounds toovercome all or some of the aforementioned shortcomings.

A further objective of the present invention is to provide a lubricantcomposition allowing the cleanliness of a 4-stroke vehicle engine to beimproved, having a formulation that is easy to implement.

A further objective of the invention is to provide a lubricantcomposition allowing an improvement in the cleanliness of a 4-strokevehicle engine and to reduce the content of detergent additives ordispersants.

A further objective of the present invention is to provide a lubricantcomposition allowing an improvement in the cleanliness of a 4-strokevehicle engine whilst maintaining good cold start properties.

The subject of the invention is therefore the use of an alcohol offormula (I)

R—OH   (I)

where R is a saturated, linear or branched alkyl group having 10 to 36carbon atoms, preferably 12 to 36 carbon atoms, more preferably 12 to 24carbon atoms, further preferably 12 to 18 carbon atomsin a lubricant composition to improve the cleanliness of a 4-strokevehicle engine.

The improved engine cleanliness of the invention is considered to be animprovement in engine cleanliness compared with that obtained by alubricant composition not containing the alcohol of the invention.

The applicant has surprisingly found that the presence of at least onealcohol of formula (I) in a lubricant composition allows improvedcleanliness of a 4-stroke vehicle engine. The applicant has also foundthat the presence of at least one alcohol of formula (I) additionallyallows good cold start properties of the lubricant to be maintained.

Advantageously, the lubricant compositions of the invention have goodcleanliness improving properties when in use in an engine, therebyallowing the content of detergent additives to be reduced in saidlubricant compositions.

Preferably, the alcohol is selected from among compounds of formula (I)where R is a saturated, branched alkyl group having 10 to 36 carbonatoms, preferably 12 to 36 carbon atoms, more preferably 12 to 24 carbonatoms, further preferably 12 to 18 carbon atoms.

The inventors have shown that an alcohol having an alkyl chain with morethan 36 carbon atoms is solid. Consequently, on cold starts thecomposition is insufficiently fluid and is therefore unable to fulfilits role. Additionally, the inventors have shown that an alcohol havingan alkyl chain with fewer than 10 carbon atoms is highly volatile.Therefore, when an engine is in use, the alcohol volatilises and isconsequently unable to fulfil its role. The choice of alcohol istherefore of essential importance in the invention.

Preferably, the alcohol of formula (I) is of formula (Ia)

R¹—C(R²)(H)—CH₂—OH   (Ia)

where R¹ and R² are saturated, linear or branched alkyls selected sothat the compound of formula (Ia) comprises 10 to 36 carbon atoms,preferably 12 to 36 carbon atoms, more preferably 12 to 24 carbon atoms,further preferably 12 to 18 carbon atoms.

The alcohols of the invention are marketed by Ecogreen Oleochemicalsunder the trade names Ecorol 12/98®, Ecorol 14/98® and Ecorol 16/98®, orby Sasol under the trade Isofol®.

Advantageously, the alcohols of formula (I) where R is branched, or thealcohols of formula (Ia) which are branched alcohols, are liquid attemperatures lower than 0° C. (low melt point), allowing optimized useof the lubricant compositions of the invention in 4-stroke vehicleengines. The lubricant compositions comprising these alcohols have goodcold start properties.

Preferably, the lubricant composition comprises from 0.1 to 10 weight %,preferably 0.1 to 4 weight %, more preferably 0.2 to 3 weight %,advantageously 0.3 to 2.5 weight % of alcohol relative to the totalweight of the lubricant composition.

The present invention also concerns a lubricant composition for 4-strokevehicle engine, comprising:

-   -   at least one base oil; and    -   at least one alcohol of formula (I) such as defined above.

The present application also concerns the use of a lubricant compositionof the invention to improve the cleanliness of a 4-stroke vehicleengine.

The invention also concerns a method for improving the cleanliness of a4-stroke vehicle engine, said method comprising at least one step tocontact a mechanical part of the machine with a lubricant compositionsuch as defined above.

The percentages indicated in the present application correspond toweight percentages of active substance.

In general, the lubricant composition used in the invention may compriseany type of lubricant base oil whether mineral, synthetic or natural,animal or vegetable, known to persons skilled in the art.

The base oils used in the lubricant compositions of the invention can beoils of mineral or synthetic origin belonging to Groups 1 to V of theclasses defined in the API classification (or equivalents in the ATIELclassification) (Table A), or mixtures thereof.

TABLE A Viscosity Saturates Sulfur Index content content (VI) Group 1 <90% >0.03% 80 ≤ VI < 120 Mineral oils Group II ≥90% ≤0.03% 80 ≤ VI <120 Hydrocracked oils Group III ≥90% ≤0.03% ≥120 Hydrocracked orhydroisomerized oils Group IV Polyalphaolefins (PAOs) Group V Esters andother bases not included in Groups 1 to IV

The mineral base oils of the invention include all types of base oilsobtained by atmospheric and vacuum distillation of crude oil, followedby refining operations such as solvent extraction, deasphalting, solventdewaxing, hydrotreatment, hydrocracking, hydroisomerization andhydrofinishing.

Mixtures of synthetic and mineral oils can also be employed.

In general, there is no limit as to the use of different lubricatingbases to produce the lubricant compositions of the invention, other thanthat they must have properties particularly of viscosity, viscosityindex, sulfur content and oxidation resistance that are adapted for usein engines or for vehicle transmissions.

The base oils of the lubricant compositions used in the invention canalso be selected from among synthetic oils such as some esters ofcarboxylic acids and alcohols, and from among polyalphaolefins. Thepolyalphaolefins used as base oils are obtained for example frommonomers having 4 to 32 carbon atoms, e.g. from octene, decene ordodecene, and having a viscosity at 100° C. of between 1.5 and 15mm².s⁻¹ in accordance with standard ASTM D445. Their molecular weightaverage is generally between 250 and 3 000 in accordance with standardASTM D5296.

Preferably, the base oils of the present invention are selected fromamong the above base oils having an aromatic content of between 0 and45%, preferably between 0 and 30%.

The aromatic content of oils is measured using the UV Burdett method.

Advantageously, the lubricant composition used in the inventioncomprises at least 50 weight % of base oils relative to the total weightof the composition.

More advantageously, the lubricant composition used in the inventioncomprises at least 60 weight %, even at least 70 weight % of base oilsrelative to the total weight of the composition.

Further advantageously, the lubricant composition used in the inventioncomprises from 60 to 99.5 weight % of base oils, preferably 70 to 99.5weight % of base oils relative to the total weight of the composition.

Numerous additives can be employed for this lubricant composition usedin the invention.

The preferred additives for the lubricant composition used in theinvention are selected from among friction modifiers, detergents,anti-wear additives, extreme-pressure additives, viscosity indeximprovers, dispersants, antioxidants, pour point improvers, defoamers,thickeners and mixtures thereof.

Preferably, the lubricant composition used in the invention comprises atleast one anti-wear additive, at least one extreme-pressure additive ormixtures thereof.

Anti-wear additives and extreme-pressure additives protect rubbingsurfaces by forming a protective film adsorbed on these surfaces.

There is a wide variety of anti-wear additives. Preferably, for thelubricant composition of the invention the anti-wear additives areselected from among phospho-sulfurized additives such as metalalkylthiophosphates, in particular zinc alkylthiophosphates, and morespecifically zinc dialkyldithiophosphates or ZnDTPs. The preferredcompounds have the formula Zn((SP(S)(OR³)(OR⁴))₂ where R³ and R⁴, thesame or different, are independently an alkyl group, preferably an alkylgroup having 1 to 18 carbon atoms.

Amine phosphates are also anti-wear additives that can be used in thelubricant composition of the invention. However, the phosphoruscontributed by these additives may act as poison for catalytic systemsof motor vehicles since these additives generate ash. These effects canbe minimised by partly substituting amine phosphates by additives thatdo not contain phosphorus such as polysulfides for example in particularsulfurized olefins.

Advantageously, the lubricant composition of the invention may comprisefrom 0.01 to 6 weight %, preferably 0.05 to 4 weight %, more preferably0.1 to 2 weight % of anti-wear and extreme-pressure additives relativeto the total weight of the lubricant composition.

Advantageously, the lubricant composition of the invention may compriseat least one friction modifying additive. The friction modifyingadditive can be selected from among a compound providing metal elementsand an ash-free compound. Among the compounds providing metal elements,mention can be made of transition metal complexes such as Mo, Sb, Sn,Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprisingatoms of oxygen, nitrogen, sulfur or phosphorus. Ash-free frictionmodifying additives are generally or organic origin and can be selectedfrom among the monoesters of fatty acids and polyols, alkoxylatedamines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides;fatty amines or fatty acid glycerol esters. According to the invention,the fatty compounds comprise at least one hydrocarbon group having 10 to24 carbon atoms.

Advantageously, the lubricant composition of the invention may comprise0.01 to 2 weight %, or 0.01 to 5 weight %, preferably 0.1 to 1.5 weight% or 0.1 to 2 weight % of friction modifying additive relative to thetotal weight of the lubricant composition.

Advantageously, the lubricant composition of the invention may compriseat least one antioxidant additive.

An antioxidant additive generally allows delayed degradation of thelubricant composition in use. This degradation may notably translate asthe formation of deposits, as the presence of sludge or as an increasein viscosity of the lubricant composition.

Antioxidant additives particularly act as radical inhibitors orhydroperoxide decomposers. Among the antioxidant additives frequentlyemployed, mention can be made of antioxidant additives of phenolic type,antioxidant additives of amino type, phosphor-sulfurized antioxidantadditives. Some of these antioxidant additives e.g. phospho-sulfurizedantioxidant additives may generate ash. Phenolic antioxidant additivesmay be ash-free or may be in the form of neutral or basic metal salts.Antioxidant additives can be selected in particular from amongsterically hindered phenols, sterically hindered phenol esters andsterically hindered phenols comprising a thioether bridge,diphenylamines, diphenylamines substituted by at least one C₁-C₁₂ alkylgroup, N,N′-dialkyl-aryl-diamines, and mixtures thereof.

Preferably, according to the invention, the sterically hindered phenolsare selected from among compounds comprising a phenol group in which atleast one vicinal carbon of the carbon carrying the alcohol function issubstituted by at least one C₁-C₁₀ alkyl group, preferably a C₁-C₆ alkylgroup, preferably a C₄ alkyl group, preferably by the tert-butyl group.

Amine compounds are another class of antioxidant additives that can beused, optionally in combination with phenolic antioxidant additives.Examples of amino compounds are the aromatic amines e.g. the aromaticamines of formula NR⁵R⁶R⁷ where R⁵ is an aliphatic group or aromaticgroup, optionally substituted, R⁶ is an aromatic group, optionallysubstituted, R⁷ is a hydrogen atom, an alkyl group, an aryl group orgroup of formula R⁸S(O)_(z)R⁹ where R⁸ is an alkylene group oralkenylene group, R⁹ is an alkyl group, an alkenyl group or aryl groupand z is 0, 1 or 2.

Sulfurized alkyl phenols or the alkali or alkaline-earth metal saltsthereof can also be used as antioxidant additives.

Another class of antioxidant additives is that of copper compounds e.g.copper thio- or dithio-phosphates, copper and carboxylic acid salts,copper dithiocarbamates, sulfonates, phenates and acetylacetonates.Copper I and II salts, the salts of succinic acid or anhydride can alsobe used.

The lubricant composition of the invention may contain any type ofantioxidant additives known to persons skilled in the art.

Advantageously, the lubricant composition comprises at least oneash-free antioxidant additive.

Also advantageously, the lubricant composition of the inventioncomprises 0.5 to 2% by weight of at least one antioxidant additiverelative to the total weight of the composition.

The lubricant composition of the invention may also comprise at leastone detergent additive.

Detergent additives generally allow a reduction in the formation ofdeposits on the surface of metal parts by dissolving secondary oxidationand combustion products.

The detergent additives that can be used in the lubricant composition ofthe invention are generally known to skilled persons. The detergentadditives can be anionic compounds comprising a long lipophilichydrocarbon chain and hydrophilic head. The associated cation may be ametal cation of an alkali or alkaline-earth metal.

The detergent additives are preferably selected from among the salts ofalkali metals or alkaline-earth metals of carboxylic acids, sulfonates,salicylates, naphthenates and phenate salts. The alkali oralkaline-earth metals are preferably calcium, magnesium, sodium orbarium.

These metal salts generally comprise the metal in stoichiometric amountor in excess i.e. an amount greater than the stoichiometric amount. Theyare then overbased detergent additives; the excess metal imparting theoverbased nature to the detergent additive is then generally in the formof an oil-insoluble metal salt e.g. a carbonate, hydroxide, an oxalate,acetate, glutamate, preferably a carbonate.

Advantageously, the lubricant composition of the invention may comprisefrom 0.5 to 4 weight % of detergent additive relative to the totalweight of the lubricant composition.

Also advantageously, the lubricant composition of the invention may alsocomprise at least one pour point depressant additive.

By slowing the formation of paraffin crystals, pour point depressantsgenerally improve the behaviour of the lubricant composition of theinvention under cold temperatures.

As examples of pour point depressant additives, mention can be made ofalkyl polymethacrylates, polyacrylates, polyarylamides,polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

Advantageously the lubricant composition of the invention may alsocomprise at least one dispersant.

The dispersant can be selected from among Mannich bases, succinimidesand derivatives thereof.

Also advantageously, the lubricant composition of the invention maycomprise from 0.2 to 10% by weight of dispersant relative to the totalweight of the lubricant composition

The lubricant composition of the present invention may also comprise atleast one additive improving the viscosity index. As examples ofviscosity index improvers mention can be made of polymer esters,homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene,butadiene and isoprene, polyacrylates, polymethacrylates (PMAs) orolefin copolymers in particular ethylene/propylene copolymers.

The lubricant composition of the invention can be in different forms. Inparticular, the lubricant composition of the invention can be ananhydrous composition.

Preferably, this lubricant composition is not an emulsion.

The above-defined lubricant composition is used to improve thecleanliness of a 4-stroke vehicle engine.

The lubricant composition for 4-stroke vehicle is preferablycharacterized by a BN lower than 15, preferably lower than 10. BN isdetermined in accordance with standard ASTM D-2896.

Preferably, contrary to lubricants for marine engines which contain atleast 5 weight % of detergent, the lubricants for vehicle enginegenerally comprise little detergent.

By vehicle engine according to the invention it is more particularlymeant vehicle engines such as:

-   -   engines of motor vehicles including gasoline engines and diesel        engines, but also engines powered by gas and gasoline (dual-fuel        gas/gasoline engines), engines powered by gas and diesel        (dual-fuel gas/diesel engines) and engines powered by gasoline        and diesel;    -   heavy vehicle engines and more specifically gas-operated heavy        vehicle engines,    -   engines of hybrid or micro-hybrid vehicles equipped with a «Stop        and Start” system.

FIG. 1: Photo of piston underside after engine testing with acomparative composition (CC1).

FIG. 2: Photo of piston underside after engine testing with acomposition of the invention (CI8).

The different aspects of the invention can be illustrated by thefollowing nonlimiting examples:

EXAMPLE 1 Lubricant Compositions of the Invention

The different components of the reference lubricant composition Cref1were mixed according to the type and amounts given in Table 1.

TABLE 1 Cref 1 (weight %) Gr III base oil (kinematic viscosity at 100°C. measured 33.9 as per standard ASTM D-556 = 4 mm²/s) Gr III base oil(kinematic viscosity at 100° C. measured 20.6 as per standard ASTM D-556= 7 mm²/s) PAO-type base oil (kinematic viscosity at 100° C. 30.0measured as per standard ASTM D-556 = 4 mm²/s) Viscosity index improver(olefin copolymer) 5.5 Pour point depressant (polymethacrylate) 0.3Friction modifier (organomolybdenum compound) 0.5 Detergent (calciumsulfonate) 0.5 Additive package comprising a dispersant of 8.7succinimide type, amine antioxidant, phenolic antioxidant, anti-wear ofzinc dithiophosphate type, detergent of overbased calcium sulfonatetype, detergent of neutral calcium sulfonate type, a silicone defoamer)

Lubricant compositions of the invention CI1, CI2, CI3, CI4, CI5, CI6,CI7 were then prepared as a function of the type and amounts (weight %)given in Table 2.

TABLE 2 Cref CI1 CI2 CI3 CI4 CI5 CI6 CI7 Cref 100 98 96 94 92 98 96 98Lauryl 2 4 6 8 alcohol¹ Myristyl 2 4 alcohol² Cetyl 2 alcohol³ ¹Ecorol12/98 ® marketed by Ecogreen Oleochemicals ²Ecorol 14/98 ® marketed byEcogreen Oleochemicals ³Ecorol 16/98 ® marketed by EcogreenOleochemicals

EXAMPLE 2 Evaluation of Improved Engine Cleanliness Properties of theLubricant Compositions of the Invention CI1 to CI7, and of the ReferenceLubricant Cref

This evaluation was performed via PCT method in accordance with standardGFC LU 029 T97 and allowed simulation of the engine cleanlinessperformance of a lubricant composition.

The results of this evaluation are given in Table 3; the higher thescore, the better the performance of the lubricant composition inimproving cleanliness.

TABLE 3 Cref CI1 CI2 CI3 CI4 CI5 CI6 Score 7.4 8 7.9 7.9 7.9 7.8 7.7

The results show that the use of an alcohol of the invention in alubricant composition improves engine cleanliness (lubricantcompositions CI1 to CI6), compared with a reference lubricantcomposition not containing an alcohol of the invention (lubricantcomposition Cref).

EXAMPLE 3 Evaluation of Improved Engine Cleanliness Properties of aLubricant Composition of the Invention CI8 and of a ComparativeLubricant Composition CC1

The different components of the lubricant composition of the inventionCI8 and of the comparative lubricant composition CC1 were mixed as afunction of the type and amounts given in Table 4.

TABLE 4 CI8 CC1 Gr III base oil (kinematic viscosity at 62 64 100° C.measured as per standard ASTM D-556 = 4 mm²/s) Gr III base oil(kinematic viscosity at 15 15 100° C. measured as per standard ASTMD-556 = 6 mm²/s) Viscosity index improver 3.5 3.5 (polymethacrylate)Viscosity index improver 2 2 (Hydrogenated polyisoprene styrene (HPIS))Pour point depressant additive 0.2 0.2 (polymethacrylate) Frictionmodifier 0.5 0.5 (organomolybdenum compound) Additive package comprisinga 14.8 14.8 dispersant of succinimide type, detergent of calciumsulfonate type, detergent of calcium carbonate type Lauryl alcohol ⁴ 2 ⁴Ecorol ®12/98 marketed by Ecogreen Oleochemicals

The engine cleanliness performance of the lubricant compositions CI8 andCC1 was evaluated with the following method.

Each lubricant composition (8 Kg) was evaluated using a cleanliness testfor a vehicle diesel engine with common rail. The engine capacity was1.4 L for 4 cylinders. Engine power was 80 kW. The test cycle length was96 hours alternating idle speed and a speed of 4 000 rpm. Thetemperature of the lubricant composition was 145° C. and the watertemperature of the cooling system was 100° C. No oil change and notopping-up of lubricant were performed during the test. EN 590 fuel wasused. The test took place in two phases for a total time of 106 hourswith a first rinsing and run-in phase for 10 hours followed by a secondstep with the evaluated composition (4 kg), and finally an endurancestep lasting 96 hours with the evaluated composition (4 kg).

After this test, the engine parts were analysed and the 4 pistonsevaluated in accordance with European standard CEC M02A78. For eachpiston the score was recorded and a mean of the total piston score forthe 4 pistons was calculated.

The results obtained are grouped together in Table 5.

The regular passing of a reference oil showed that a difference of 4points between two candidates is significant.

The higher the value of the mean score the better the improvedcleanliness of the piston, and hence the better the performance of thelubricant composition in improving engine cleanliness.

TABLE 5 Evaluated composition Mean piston score after testing CI8 68.5CC1 61.6

The results confirm those of Example 2 regarding the improvement inengine cleanliness afforded by a lubricant composition comprising analcohol of the invention (lubricant composition CI8), in comparison witha lubricant composition not containing an alcohol of the invention(lubricant composition CC1).

In addition, it is also shown in FIGS. 1 and 2, after this test, thatthe piston undersides are clean i.e. there was no deposit whencomposition CI8 was used (FIG. 2), unlike composition CC1 for whichfouling of the piston undersides was observed (FIG. 1).

EXAMPLE 4 Evaluation of Improved Engine Cleanliness Properties of aLubricant Composition of the Invention CI9, and of a ComparativeLubricant Composition CC2

The different components of the lubricant composition of the inventionCI9 and of the comparative lubricant CC2 were mixed as a function of thetype and amounts given in Table 6.

TABLE 6 CI9 CC2 Gr III base oil (kinematic viscosity at 71.1 72.1 100°C. measured as per standard ASTM D-556 = 4 mm²/s) Gr III base oil(kinematic viscosity at 10.8 10.8 100° C. measured as per standard ASTMD-556 = 8 mm²/s) Viscosity index improver 5.7 5.7 (polymethacrylate)Pour point depressant additive 0.2 0.2 (polymethacrylate) Frictionmodifier 0.8 0.8 (organomolybdenum compound) Additive package comprisinga 10.4 10.4 dispersant of succinimide type, detergent of calciumsulfonate type, detergent of calcium carbonate type Lauryl aclcohol⁵ 1⁵1-dodecanol marketed by Sigma Aldrich

The engine cleanliness performance of lubricant compositions CI9 and CC2were evaluated with the Sequence IIIG method in accordance with standardASTM D7320 under the following test conditions:

Parameters Engine speed 3600 rpm Engine load 250 N-m Oil temperature ofoil filter 150° C. Outgoing temperature of coolant 115° C. Fuel pressure377.5 kPa Incoming air temperature 35° C. Incoming air pressure 0.05 kPaAir dewpoint temperature 16.1° C. Exhaust counter-pressure 6 kPa Coolantflow rate 160 L/min Condenser coolant flow rate 10 L/min Air/fuel ratio15.0:1 Temperature of condenser coolant 40° C.

After this test, the engine parts were analysed and rated in the mannerdescribed in the procedure published in ASTM D7320.

The results of this test are given in Table 7 for compositions CI9 andCC2 respectively. The higher the score the better the performance of thelubricant composition in improving cleanliness.

TABLE 7 CC2 CI9 Mean of total score 4.28 4.76 Final result

The results show that the use of an alcohol of the invention in alubricant composition allows an improvement in engine cleanliness(lubricant composition CI9) compared with a reference composition notcontaining an alcohol of the invention (lubricant composition CC2).

EXAMPLE 5 Study on Cold Start Properties

The compositions in Table 8 were tested for their cold start properties:

TABLE 8 CC3 CI10 CI11 CI12 Base oil 74.1 73.6 73.1 72.1 Additives 11.311.3 11.3 11.3 Viscosity index 14.3 14.3 14.3 14.3 improver Pour point0.3 0.3 0.3 0.3 depressant 2-Butyloctanol⁶ 0 0.5 1 2 ⁶ISOFOL C12 ®alcohol of formula (Ia) in C12.

The results obtained are given in Table 9.

TABLE 9 Standards CC3 CI10 CI11 CI12 KV40 ISO 3104 93.67 90.92 88.9185.04 (mm² · s⁻¹) KV100 ISO3104 14.18 13.94 13.7 13.26 (mm² · s⁻¹) VIISO2909 156 157 157 157 CCS at ASTM 5390 5280 5150 4930 −35° C. D5293(mPa · s) MRV (cP) ASTM 24060 22630 21580 20460 D4684

Specifically, in the Mini Rotary Viscometer (MRV) test, the viscosity ofthe compositions of the invention was lower than in the comparativecomposition. This MRV test allows simulation of engine lubricationconditions on cold starts and in particular the pumpability of thelubricant on cold starts. The compositions of the invention thereforehave better cold pumpability than compositions not containing a fattyalcohol.

Also specifically, in the Cold Cranking Simulator (CCS) test, thefluidity of the compositions of the invention was lower than in thecomparative composition. This CCS test allows simulation of enginelubrication conditions on cold starts, and in particular the fluidity ofthe lubricant on cold starts allowing ignition of the engine. Thecompositions of the invention therefore have better cold start fluiditythan the compositions not containing a fatty alcohol.

These results show that the branched alcohols of the invention affordimproved cold start properties of the lubricant.

1. A method for improving the cleanliness of a 4-stroke vehicle enginecomprising the lubrication of the engine with a lubricant compositioncomprising an alcohol of formula (I)R—OH   (I) where R is a saturated, linear or branched alkyl group having10 to 36 carbon atoms, in a lubricant composition to improve thecleanliness of a 4-stroke vehicle engine.
 2. The use according to claim1, wherein the alcohol is selected from among the compounds of formula(I) where R is a saturated, linear or branched alkyl group having 12 to36 carbon atoms.
 3. The method according to claim 1, wherein the alcoholis selected from among the compounds of formula (Ia)R¹—C(R²)(H)—CH₂—OH   (Ia) where R¹ and R² are saturated, linear orbranched alkyls selected so that the compound of formula (Ia) comprises10 to 36 carbon atoms, preferably 12 to 36 carbon atoms.
 4. The methodaccording to claim 1, wherein the lubricant composition comprises atleast one base oil.
 5. The method according to claim 1, wherein thelubricant composition comprises from 0.1 to 10 weight %, preferably 0.1to 4 weight %, more preferably 0.2 to 3 weight %, advantageously 0.3 to2.5 weight % of alcohol relative to the total weight of the lubricantcomposition.
 6. (canceled)